1. Field of the Invention
The present invention relates to an image processing apparatus, and more particularly, relates to an image processing apparatus and method for correcting a blur due to aberration of an optical system, such as an image capturing apparatus.
2. Description of the Related Art
In the field of an image capturing apparatus, such as digital cameras, it is known that an aberration of an optical system causes an image deterioration such as image blur. Japanese Patent Application Laid-Open No. 2001-197354 and Japanese Patent No. 3,532,368 discuss image restoration techniques to restore this image deterioration using Point Spread Function (PSF) of the optical system.
An aberration characteristic of an optical system varies depending on pixel positions in an image. Therefore, it is required to change a restoration operation depending on pixel positions in an image. Japanese Patent Application Laid-Open No. 2001-197354 discusses an image restoration technique where different filters are applied to all pixels in an image. This image restoration technique provides preferred filters for every pixel position in an image. However, a vast amount of computational cost is required to generate the filters for all pixel positions in an image using Fourier transform. Moreover, large scale memory equipment is needed to store the generated filters.
Japanese Patent No. 3,532,368 discusses another image restoration technique where (a) an image is divided into a plurality of regions in a concentric fashion, and (b) different filters are applied to each of the divided regions. This is because the aberration characteristic of an optical system is symmetric with respect to an optical center of an image. Since a common filter is used in respective divided regions, the computational cost to generate filters and the memory size to store the filters can be reduced. However, this technique may not deal with the variation of the aberration characteristic over the image since constant filters (common filters) are applied to each region. Moreover, artifacts are generated at the border between the divided regions.